The invention relates to a filter ring to be inserted in ring-shaped apertures or openings in the wall of hollow bodies containing or through which gases or liquids flow, the filter ring having a slit in its wall, which surrounds a hollow space, the slit extending parallel to the ring axis along the entire axial length of the ring, wherein the wall portions of the ring located to both sides of this slit are joined with one another by a snap lock. A filter ring of this kind is being brought onto the market by the applicant for several months.
Filter rings of this type are as a rule inserted in grooves arranged on the outer side of the wall of the hollow body, for example the wall of a pipe, the groove being provided in the region of the aperture or opening of the hollow body wall. For insertion into these grooves, the filter rings must be widened or opened to enable them to be pushed over the outer wall of the hollow body. The slit provided in the previously mentioned, known filter ring extending over the entire axial length of the ring is provided for this purpose, the slit enabling a separation of the ring wall at one peripheral location of the filter ring and thus enabling the widening of the filter ring to a ring diameter which allows the ring to be pushed over the outer surface of the hollow body. After the insertion of the filter ring into the groove, the pushing together of its wall portions located to both sides of the slit and the secure joining of these by means of the snap lock, the ring can be closed and returned to its initial diameter which corresponds to the diameter of the base of the groove.
In the known filter ring, the snap lock is formed by means of a catch rib which is arranged on one wall portion of the ring, extends over the entire axial length of the ring and which can catch in a groove equally arranged and extending over the other wall portion. As the catch should be secure, the side surfaces of the catch rib and the catch groove lying opposite one another are undercut in such a manner that they grip into each other (clip lock). However, this design requires a relatively large wall thickness of the ring, as the undercut catch rib and groove are not practical in a thin-walled ring for reasons of space and fastness.